(i) Field of the Invention
The present invention relates to an electric noise absorber which is attached around an electric wire of electronic apparatus to absorb electric noise flowing through the electric wire.
(ii) Description of the Related Art
In a conventional art electric noise absorber of this kind, two magnetic body parts, which are configured to collectively form a tubular magnetic body for encompassing the circumference of an electric wire, are housed in a plastic holding case.
The electric noise absorber is attached around the electric wire so as to grip the electric wire from both sides, so that the magnetic body parts, which are held in a tubular shape with their abutting surfaces closely contacting each other and absorb electric noises flowing through the electric wire.
In such an electric noise absorber comprising abutting magnetic body parts, if the contact between the magnetic body parts is loose when the holding case is closed, the magnetic body parts are unsteady and may be broken by striking each other. Therefore, measures are taken in order to make the magnetic body parts press each other and ensure close contact between the abutting surfaces thereof, thereby preventing unsteadiness of the magnetic body parts. One such measure is to provide tongue-like spring members projecting from the inner surface of the side walls of the holding case toward the housing space, and another is to insert curved leaf springs between the holding case and the magnetic body parts.
When spring members are used, however, not only is the strength of the holding case decreased, because the spring members are formed by notching the outer walls of the case, but also since the spring members pressed by the magnetic body parts are exposed to continuous stress, the spring members are apt to be permanently deformed due to stress-creep when left in that state for a long time and gradually lose pressure against the magnetic body parts.
In the case where leaf springs are used, the manufacturing and assembly operation requires more tie and labor due to the increase of the number of parts.
Wherefore, an object of the present invention is to provide an electric noise absorber which can prevent unsteadiness of the magnetic body parts when its holding case is closed, without increasing the number of parts or decreasing the strength of the holding case.
To accomplish the above object, the present invention discloses an electric noise absorber for attachment around an electric wire of electronic apparatus to absorb electric noises flowing through the electric wire. The electric noise absorber comprises: a pair of magnetic body parts together defining a hollow cylinder to encompass the circumference of the electric wire; and a holding case, including case halves for housing the magnetic body parts, respectively, and connecting members for releasably connecting the case halves. The holding case holds the magnetic body parts in the shape of a hollow cylinder when the case halves are in a closed position. Circumferential walls of the case halves are formed such that those walls are deformed by being pressed by the magnetic body parts when the holding case is closed, so that the resilience of the deformed circumferential walls to return to the former shape causes force to urge the abutting surfaces of the magnetic body parts into close contact with each other.
As described above, with the electric noise absorber according to the invention, unsteadiness of the magnetic body parts in the holding case is prevented.
Moreover, the electric noise absorber according to the invention can prevent reduction of the strength of the holding case or increase of time and labor for manufacturing and assembly operation because it is not necessary to notch the case halves or to add any other parts.
A specific shape of the circumferential walls of the case halves having the aforementioned effects and advantages is, for example, a curved shape convex toward the housing space for housing the magnetic body parts. In this case, the magnetic body parts housed in the housing space are formed such that, when the magnetic body parts contact with the most protruding parts of the circumferential walls, the abutting surfaces of the magnetic body parts extend out of the edge surfaces (hereinafter referred to as xe2x80x9copen mouth surfacesxe2x80x9d) of the case halves. When the holding case is closed, the extending portions of the magnetic body parts are pressed into the case halves, which results in deformation of the curved circumferential walls outward. As a result, the resilience of the circumferential walls to return to the former shape causes force to urge the abutting surfaces of the magnetic body parts into close contact with each other.
Such resilience can also be obtained in other ways, as long as the circumferential walls can be deformed by contacting the magnetic body parts when the holding case is closed.
For example, the inner surface of the circumferential walls of the case halves may be provided at the axial center thereof with protrusions which protrude toward the housing space for housing the magnetic body parts. Also in this case, as long as the magnetic body parts are formed such that the abutting surfaces of the magnetic body parts in contact with the protrusions extend from the xe2x80x9copen mouth surfacexe2x80x9d of the case halves when the magnetic body parts are inserted in the case halves, the same effects and advantages as aforementioned can be obtained.